1. Field of the Invention
The present invention relates generally to optical systems, and more particularly to an apparatus and method for bonding and fixing optical elements in a liquid crystal shutter.
2. Brief History of the Art
Certain applications of liquid crystal devices require the incorporation of two or more rectangular optical elements in their fabrication. One example of such a device is a double super twist cell which consists of an active LCD cell and a compensating LCD cell. Another example of such a device is a liquid crystal display shutter which requires the use of two .pi.-cells, and, in some applications, a third anti-reflection sheet of glass. In the case of the liquid crystal shutter, the shutter is often used in a color display which includes a CRT raster device, another element forming the optical system.
In the above-described applications, it is highly desirable to accurately register the optical elements relative to one another using an inexpensive procedure suitable for high volume manufacturing. Contemporary optical system solutions are inadequate in this context. For example, in one common type of solution, a dismantlable mold is used during manufacture to place each optical element in its appropriate relative position. An optically based gel or epoxy, in its pre-cured state, is then poured over a single element before the next element is overlaid. The entire assembly is then cured. After each operation, the optical assembly must be removed and any extraneous material must be removed. There is also extraneous cured material which must be removed from the molding fixture after each cure cycle making this process slow, expensive and poorly suited for high volume manufacturing.
In another equally inadequate contemporary solution, a shutter is mounted in position in the display assembly and the CRT is normally mounted separately, leaving an air space between the CRT and shutter. Because there is no form of enclosure surrounding the system, dust rapidly settles on the optical elements causing a degradation in optical coupling efficiency and a loss of light transmitted through the optical assembly.